Prior charge pumps have almost the full supply voltage across one the output transistors when the output voltage of the charge pump output voltage is either near ground or near the supply. This limits the charge pump supply voltage to slightly more than the maximum operating voltage of the devices used to implement the charge pump. As geometries of semiconductor devices have decreased, the design of voltage control oscillators have had to trade off smaller design geometries with increased voltage to frequency constants of the VCO. However, the increased voltage to frequency constant is associated with increased phase noise and decreased VCO performance.
Thus, there is a need for an improved charge pump design to permit implementation of charge pump circuits with smaller geometry semiconductor devices.
Summary of the Disclosure
The present disclosure relates to a charge pump. One exemplary charge pump includes a first pass transistor and a second pass transistor coupled to create a charge pump output. A first controlled current source is coupled to the first pass transistor and a second controlled current source is coupled to the second pass transistor. A tracking circuit receives the charge pump output and provides two reference voltages. The first reference voltage is coupled to the well of the first pass transistor. The second reference voltage is coupled to the well of the second pass resistor. The tracking circuit is configured to track the charge pump output in order to regulate the voltages across the first pass transistor and the second pass transistor.
Another example charge pump includes generating a charge pump voltage output with a first pass transistor and a second pass transistor. A potential between a well voltage of the first pass transistor relative to the charge pump voltage output and the potential between the charge pump output voltage and a well voltage of the second pass transistor are controlled to be substantially the same.
Those skilled in the art will appreciate the scope of the disclosure and realize additional aspects thereof after reading the following detailed description in association with the accompanying drawings.